‘ Biologic Forms' of the Erysiphciceae. 143 
On the tenth day a few tiny flecks of mycelium bearing a few conidiophores 
were visible on the three barley leaves which had been heated ; no trace of 
any infection occurred on the three control barley leaves. On the thirteenth 
day the three heated barley leaves bore numerous little scattered clusters 
of conidiophores. Conidia from these leaves were sown in two cases on 
uninjured leaves of barley and of wheat, and proved able to infect only 
the wheat. 
In experiment No. #013, six barley leaves were rubbed in water 
to remove the film of air adherent to their surface, and then immersed for 
1 minute in water at the temperature of 50° C. The leaves were then 
plunged into cold water for a minute, then dried, and inoculated with 
conidia. No trace of infection resulted on any of the leaves. 
In another experiment (No. a 022) twelve barley leaves were cut off 
from seedlings of the same age, growing in one pot ; six leaves were 
immersed for 1 minute in water at the temperature of 50° C., and then 
dried rapidly by blotting paper ; all twelve leaves were then inoculated. 
On the eighth day three of the leaves which had been heated bore numerous 
little clustered groups of conidiophores ; on one control leaf three isolated 
conidiophores were visible among the sown conidia. On the fourteenth 
day one of the leaves which had been heated bore numbers of scattered, 
whitish, quite powdery little clusters of conidiophores over the inoculated 
place. The conidia were sown, in fair quantity, on an uninjured leaf of 
barley and of wheat, and proved able to infect only the wheat. In one 
experiment (No. #018) twenty seedlings of barley, growing in a pot, were 
dipped for 1 minute into water at a temperature of 50° C. in such a way as 
to immerse all the leaves. All the leaves were then inoculated abundantly 
with conidia. A control pot of barley seedlings after inoculation was placed 
by the side. On the fifth day several of the leaves of the treated plants 
bore numerous flecks of mycelium with a few young conidiophores. On the 
ninth day six leaves bore minute flecks of mycelium, bearing small patches 
of clustered conidiophores, in a few cases forming a small powdery Oidium- 
patch ; many barren mycelial flecks were present on several other leaves. 
No trace of any infection appeared on the control plants. On one leaf 
the little Oidium - patch kept powdery until the sixteenth day, producing 
successive crops of conidia. (These conidia were sown on two uninjured 
leaves of barley and on one uninjured leaf of wheat, and proved able to 
infect only the wheat.) All traces of the primary infection, however, 
gradually disappeared by the end of the third week of the experiment, 
and no signs of any secondary infection from the conidia produced were 
observed. 
In experiment No. <205, three barley leaves were immersed for 
1 minute in water at 49-5° C. On the fifth day all the leaves presented the 
appearance of being fully infected, the Fungus having produced very 
